This invention relates generally to a ribbon feed mechanism for a bi-directional printer, and more specifically to a ribbon feed mechanism that provides a constant relative velocity between the ribbon and a horizontally traversable print head. Modern printers commonly print in both left-to-right and right-to-left directions. Depending on the type of the printer ribbon, it is desirable and often necessary to maintain fresh ribbon at the printing point. Present methods accomplish this result by maintaining the ribbon at a constant velocity relative to the stationary paper, regardless of the velocity (or direction) of the print head. This operation produces two undesirable results. First, variations in relative ribbon to print head velocity cause color density variations which detract from the printed document's appearance. Second, a relatively large volume of ribbon has to be passed through the system.
Among the several objects of this invention is to provide a ribbon feed system for a printer which prints at high speeds in both directions and produces a uniform and acceptable color density in all phases of printing; to provide such a system that utilizes a very high percentage of the length of a ribbon; to provide such a system which is of relatively simple and inexpensive construction, and which may be easily incorporated into the design of printers of standard design.